Strategies that confer self-healing properties may extend the applications of ceramic materials. Catastrophic foreign object damage and consequently unpredictable lifespan limit the application of most monolithic ceramics in high-speed rotating blades operating at high temperatures 10. However, even these advanced ceramics remain unsuitable for use in turbine blades, which have strict safety requirements. Recent damage-resistant ceramics 4– 8 are optimised for high-temperature applications and have reinforcing hierarchical architectures 4– 9. For example, structural ceramics with high specific strength and rigidity, and excellent heat resistance are strong candidates for use as turbine blades in aircraft engines, particularly given the industry-wide focus on fuel efficiency 1– 3. Lightweight, self-healing ceramics would greatly increase fuel efficiency in aircraft. Our design strategy can be applied to develop new lightweight, self-healing ceramics suitable for use in high- or low-pressure turbine blades in aircraft engines. Based on bone healing, we here named these stages as inflammation, repair, and remodelling stages, respectively. We also clarified that the healing mechanism could be divided to the initial oxidation and additional two stages. Furthermore, the activator promotes crystallisation of the melts and forms a mechanically strong healing oxide. The activator on the fracture path exhibits rapid fracture-gap filling by generation of mobile supercooled melts, thus enabling efficient oxygen delivery to the healing agent.
We demonstrate that addition of a small amount of an activator, typically doped MnO localised on the fracture path, selected by appropriate thermodynamic calculation significantly accelerates healing by >6,000 times and significantly lowers the required reaction temperature. Here, we report a new approach for a self-healing design containing a 3D network of a healing activator, based on insight gained by clarifying the healing mechanism. Self-crack-healing by oxidation of a pre-incorporated healing agent is an essential property of high-temperature structural ceramics for components with stringent safety requirements, such as turbine blades in aircraft engines.
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